GCSE Chemistry: the rate and extent of chemical change

These flashcards cover key concepts related to atomic structure and the periodic table as part of GCSE Chemistry.

Rate of Reaction

How quickly the reactants are turned into products.

Rate Calculation

Rate = amount of reactant used or product formed over time.

Units of Rate

g/s, cm/s, or mol/s depending on the context.

Measuring Rate of Reaction

By measuring changes in mass, volume of gas produced, or visual changes (e.g. color, precipitate).

Common Experiment for Gas Production

Using a gas syringe or measuring cylinder over water.

Change in Mass Measurement

By placing the reaction on a balance and recording mass loss.

Factors Affecting Rate of Reaction

Temperature, concentration/pressure, surface area, and presence of a catalyst.

Effect of Temperature on Rate

Higher temperature increases particle energy, leading to more frequent and energetic collisions.

Effect of Concentration on Rate

Higher concentration means more particles in the same volume, increasing collisions.

Effect of Pressure on Rate

Higher pressure compresses gas particles, increasing collision frequency.

Effect of Surface Area on Rate

More surface area (e.g. powdered solid) exposes more particles to react.

Catalyst

A substance that speeds up a reaction without being used up by providing an alternative reaction pathway with lower activation energy.

Collision Theory

Particles must collide with sufficient energy to react.

Activation Energy

The minimum energy needed for a successful collision.

Steep Slope on Rate-Time Graph

Indicates a fast reaction.

Flat Line on Rate Graph

Indicates the reaction has stopped; no more reactants left.

Finding Rate from a Graph

By finding the gradient (change in y over change in x).

Reversible Reaction

A reaction where the products can react to reform the reactants.

Dynamic Equilibrium

When the forward and reverse reactions occur at the same rate in a closed system.

Equilibrium Meaning

The concentrations of reactants and products remain constant.

Le Chatelier's Principle

If a system at equilibrium is disturbed, it will shift to oppose the change.

Effect of Increased Reactant Concentration

The equilibrium shifts to the right to make more products.

Effect of Increased Pressure

Equilibrium shifts to the side with fewer gas molecules.

Effect of Increased Temperature

Equilibrium shifts in the endothermic direction.

Effect of Decreased Temperature

Equilibrium shifts in the exothermic direction.

Haber Process

The industrial process to make ammonia from nitrogen and hydrogen.

Conditions for the Haber Process

450°C, 200 atm, iron catalyst.

Balanced Equation for the Haber Process

N + 3H2 ⇌ 2NH3.

Compromises Made in Industry

To balance rate, yield, and cost effectively.